X-ray equipment used in the medical field typically includes a rotating anode X-ray tube. Such X-ray tubes are vacuum tubes each including a rotor having a rotatable shaft and each also including a stator which circumferentially surrounds, or is circumferentially surrounded by, the rotatable shaft. A pair of bearings, such as rolling element bearings (e.g., ball bearings), is positioned radially between the shaft and the stator. An X-ray target, which typically is attached to the rotatable shaft, is heated to high temperatures by the impinging electrons emitted by the cathode. The bearings are poor thermal conductors which sets up a temperature differential between the shaft side and the stator side of the bearings causing bearing misalignment and wear which shortens the operating life of the X-ray tube. During rotation, the bearings are prone to electrical arcing which is a disadvantage in designs requiring a stable electrical path between the shaft and the stator. Known designs include those which use bearings for rotational support and which also use liquid metal (such as gallium) in the annularly-cylindrical gap between the shaft and the stator to conduct heat and electricity. Such liquid metal equalizes the temperature on both sides of the bearing which increases bearing life, but such designs are prone to leakage of the liquid metal out of the gap with such escaped liquid metal causing high voltage instability which shortens the operating life of the X-ray tube.
What is needed, for X-ray tubes employing liquid metal for thermal and/or electrical conduction purposes, is an improved X-ray tube design which prevents leakage of the liquid metal from the gap between the shaft and the stator.